On the other high cliff opposite to this, beyond the town, has been another _Pharos_: some part of the bottom part of it is still left, called The Devil’s Drop, from the strength of the mortar: others call it Bredonstone. Here the new constable of the castle is sworn. If we consider the ancient state of Dover, we must imagine that the little river ran directly into the sea, and left a harbour close to the walls of the town; but in process of time, as the sea threw up that vast beach which lies between the town and it, the river was forced by an oblique passage to creep along the shore under the southern cliff, and there vent itself where now is the harbour. This is what Nature practises in the microcosm in innumerable instances, as the passage of the gall and pancreatic juice into the intestines, in the duct of the urine from the ureters into the bladder, of the chyle into the torrent of the blood, insinuating themselves for some space between the membranes. And this caution may be of service in forming harbours; as in that costly work of the French king’s before Dunkirk, where two banks or piers projected for half a mile through the sands directly, which ought rather to have gone downwards a little towards the fall of the tide. The cliffs here are of solid chalk to the very bottom, full of the blackest flints; and those at Calais seem perfectly like them; and no doubt a long vein of chalk is continued from one to the other under the sea, and perhaps through many countries: but that these two places were ever contiguous, or joined by an isthmus, is chimerical. Though the mariners have much mathematics on board, and in all their tackle and machinery, yet here I had occasion of observing a gross error, that has not been thought on, in the shape of their oars; where the extremity of that fan-like part, which opposes the water in rowing, is broadest. Now this is quite contrary to Nature’s method, who is the best geometrician in like cases: in the shape of a single feather, or in the wings of birds, the extremity is always pointed, and the broadest part is nearest the joint where the power lies, analogous to the _fulcrum_ of leavers; therefore is drawn off to a narrower scantling, as the part recedes from it, and the effect of the moving force: thus it is even in the wings of butterflies, and all other insects, as well as birds; and so in the water-beetles that row with oars. Though the broad part resists the water more as farther distant from the _fulcrum_, yet it requires more proportionable strength; and in my judgment, therefore, oars ought to be made quite the contrary way, and drawn off into a point, the broadest part nearest the hand; and I doubt not but equal strength will then out-row the other, _cæteris paribus_.[122]